This invention relates to an image forming apparatus that forms an image on a light-sensitive material and which transfers said image onto a receiving material. More particularly, the invention relates to an image forming apparatus that is capable of selection from a plurality of light-sensitive materials and image-receiving materials and which yet has a capability for efficient formation of high-quality image irrespective of which combination of light-sensitive and image-receiving materials is selected.
An image forming apparatus is known that performs scan exposure on a color document to form a latent image on a light-sensitive material, which is then placed in superposition on a receiving material and subjected to thermal development and transfer so that the developed image is transferred onto the receiving material, followed by separating the light-sensitive material to leave a hard copy on the receiving material.
To copy the image of color reflection-type originals such as printed matter and photographs with such image forming apparatus by a certain exposure technique, say, slit scan exposure, a latent image is first formed by scanning with an exposure unit that comprises in combination a linear scanning head for issuing illuminating light, a plurality of mirrors, light modifying color filters and diaphragm, imaging lenses, etc.
Stated specifically, the linear scanning head is moved in a direction generally perpendicular to its length so that the reflection-type original placed on the document platen is scanned two-dimensionally with slit light. The slit light reflected from the original is guided by the plurality of mirrors to travel in a pre-determined optical path and, after being adjusted for its colors and quantity by means of the color filters and diaphragm and for the imaging position, magnification, etc. by means of the imaging lens, the light is admitted and focused at the position of image-wise exposure of the light-sensitive material which is moving at a predetermined speed in a direction associated with the movement of the scanning head, thereby completing the process of exposure of the light-sensitive material.
The slit exposed light-sensitive material is then coated with an image forming solvent such as water or alcohol and placed into a superposed relationship with an image receiving material, with the combination being transported to a thermal development and transfer unit.
The thermal development and transfer unit is composed of a heating drum and an endless belt wound onto the drum. The combination of the light-sensitive and image-receiving materials is transported as it is held between the drum and the endless belt either continuously or intermittently as required, whereby the image on the light-sensitive material is developed and transferred onto the receiving material.
After the end of thermal development and transfer, the light-sensitive material is separated from the image-receiving material and ejected into a disposal tray, whereas the image-receiving material is transported to a recovery tray and used as a hard copy.
This is the process of image formation by thermal development and transfer, in which the light-sensitive material coated with an image forming solvent is placed into a superposed relationship with the receiving material and then subjected to thermal development and transfer. With the recent increase in the versatility of the application of hard copies, the scope of documents to be copied has expanded from the conventional reflection-type originals such as printed matter and photographs to various other types including transmission-type originals such as negatives and reversal films and, accordingly, many types of light-sensitive materials have become available, including positive-acting types, negative-acting types and high-density types which have high gamma (gradation) values.
This is also true with image-receiving materials and various types have become available in accordance with the specific use of hard copies. For example, there are used today not only thick- and thin-gage papers but also OHP paper which is used as the original for overhead projectors (OHPs). It has even become possible to select glossy or nonglossy thick- or thin-gage papers.
With such image forming apparatus that relies upon thermal development and transfer using more than one kind of light-sensitive and image-receiving materials, it is necessary to make temperature adjustments not only for the image forming solvent but also for the performance of thermal development in accordance with the specific combination of light-sensitive and image-receiving materials.
The efficiency of color formation varies with different light-sensitive materials and if the image of the same original is reproduced with different light-sensitive materials under the same conditions of development, the color density will vary with the specific light-sensitive material used, thereby producing images having different colors and densities.
Furthermore, the image forming apparatus that relies upon thermal development and transfer performs these steps with the light-sensitive material placed in superposed relationship with the image-receiving material.
The thickness (heat conductivity), surface properties and other characteristics of the image-receiving material vary with its type and, therefore, if the image of the same original is reproduced on different receiving materials under the same conditions of development, the efficiency of thermal development and image transfer will fluctuate, thereby producing images having different colors and densities.
Under the circumstances, the conventional image forming apparatus is so adapted that not only temperature of an image forming solvent such as water but also the temperature for thermal development is adjusted to perform image formation under the conditions of thermal development and transfer that are suited for the specific combination of light-sensitive and image-receiving materials, thereby insuring that image of high quality will be formed consistently irrespective of which combination of light-sensitive and image-receiving materials is selected.
Therefore, if one wants to change the kind of the light-sensitive material or image-receiving material to be used on this conventional apparatus, he has to wait until the temperature of the image forming solvent or the temperature for thermal development becomes best suited for the specific kind of the light-sensitive material or image-receiving material or their combination. In fact, however, such temperature adjustments are rather time-consuming and make it difficult to perform the desired image formation in a rapid and efficient manner.